On  the  (Constitution  of  Certain  Organic 
Salts  of  Nickel  and  Cobalt  as  they 
Exist  in  Aqueous  Solution. 


By  O.  F.  Tower* 


("Reprinted  from  the  Journal  of  the  American  Chemical  Society,  \ 

Vol.  XXIV,  No.  io.  October,  1902. 

ON  THE  CONSTITUTION  OF  CERTAIN  ORGANIC  SALTS 
OF  NICKEL  AND  COBALT  AS  THEY  EXIST 
IN  AQUEOUS  SOLUTION.1 

By  O.  F.  Tower. 

Received  July  2,  1902. 

It  has  been  shown  in  a former  paper  that  the  molecular  con- 
ductivities of  aqueous  solutions  of  nickel  and  cobalt  tartrates  are 
exceptionally  small,  and  furthermore  that  the  apparent  molecular 
weights  derived  from  the  freezing-point  method  considerably  ex- 
ceed the  molecular  weights  calculated  from  the  simple  formulas  of 
the  salts.2  It  was  suggested  that  these  unusual  results  could  be 
accounted  for  oh  the  assumption  of  polymerization.  The  formula, 

COONiOOC 

I I 

CHOH  CHOH 

I I 

CHOH  CHOH 

I I 

COONiOOC 

was  given  as  expressing  possibly  the  constitution  of  a molecule  of 
nickel  tartrate.  Such  a molecule  would  very  likely  be  much  less 
dissociated  in  solution  than  a simple  molecule.  In  order  to  investi- 
gate this  problem  more  fully  these  same  methods  have  been  ap- 
plied to  the  tartrates  of  other  metals  and  to  the  nickel,  cobalt,  and 
magnesium  salts  of  certain  other  organic  acids. 

These  salts  were  prepared  from  pure  chemicals  of  standard 
make.  The  solutions  were  made  by  treating  an  excess  of  the 
carbonate  or  oxide  of  the  metal  with  a sufficiently  dilute  solution 
of  the  acid.  In  a few  instances  the  hydroxide  of  the  metal  was 
employed.  On  account  of  the  slight  solubility  of  most  of  these 
organic  salts,  the  quantity  of  salt  in  solution  after  the  acid  had 
become  neutralized  was  almost  never  equivalent  to  the  quantity  of 
acid  taken,  because  some  of  the  salt  was  precipitated  while  the 
action  was  going  on.  It  was  therefore  necessary  to  determine  the 
amount  of  salt  actually  present  in  the  solution  in  each  case.  The 
temperature  of  the  solution  has  considerable  effect  on  the  solubility 

1 Read  at  the  Pittsburg  meeting  of  the  American  Chemical  Society. 

2 Tower  : This  Journal,  22,  501  (1900). 


ORGANIC  SALTS  OF  NICKEL  AND  COBALT. 


IO13 


of  these  salts.  This  effect  has  already  been  described  for  nickel 
and  cobalt  tartrates,1  and  is  similar  for  the  other  salts  used, 
although  in  most  cases  less  pronounced.  Heat  seemed  to  decrease 
the  solubility,  so  that  all  solutions  were  made  up  in  the  cold  or  at  a 
temperature  not  exceeding  50°.  The  action  of  the  dilute  acids 
was  very  slow  at  these  low  temperatures.  To  accelerate  it  the 
solution  was  constantly  shaken  until  the  reaction  was  neutral. 
This  required  only  about  fifteen  minutes  with  magnesia  and  the 
freshly  precipitated  hydroxides  of  nickel  and  cobalt,  while  for  the 
carbonates  of  nickel  and  cobalt  an  hour  or  more  was  frequently 
necessary.  Solutions  of  barium  tartrate  were  prepared  by  neu- 
tralizing a solution  of  barium  hydroxide  with  tartaric  acid.  Solu- 
tions containing  more  than  1 gram-molecule  of  barium  tartrate  in 
80  liters  were  supersaturated.  Measurements  with  these  super- 
saturated solutions  revealed  no  abnormal  behavior,  which  is  also 
the  experience  of  others.  Attempts  were  made  to  prepare  solu- 
tions of  calcium  and  zinc  tartrates.  These  salts  are,  however,  so 
insoluble  that  the  solutions  obtained  were  too  weak  to  render  the 
measurements  of  any  value  for  the  purpose  of  comparison. 

The  measurements  of  the  electrical  conductivity  of  the  tartrates 
reported  in  my  former  article  were  made  with  a small  combination 
Wheatstone-Kohlrausch  bridge  only  25  cm.  long.  All  the  meas- 
urements which  follow  were  made  with  a meter  bridge,  which  had 
been  carefully  calibrated.  The  conductivities  of  the  tartrates  of 
nickel  and  cobalt  were  therefore  redetermined  with  the  new  appa- 
ratus. The  temperature  at  which  all  the  determinations  were 
made  was  180  ± o.i°.  The  conductivity  of  the  water  used  varied 
from  2.0  to  3.0  X I0~6.  This  has  been  deducted  from  the  specific 
conductivity  in  every  case.  The  results  with  the  salts  of  tartaric, 
malic  and  succinic  acids  are  given  in  Table  I : v is  the  number  of 
liters  in  which  a gram-molecule  of  the  salt  was  dissolved ; M is 
the  molecular  conductivity  in  reciprocal  ohms.  In  the  former 
article  the  equivalent  conductivity  was  given,  but  since  some  of  the 
salts  probably  exist  in  a polymerized  condition,  the  molecular  con- 
ductivity is  given  as  affording  a better  basis  of  comparison. 

1 Tower  : loc.  at.,  pp.  504  and  515. 


1 13  q-  3 3 


ioi4 


O.  F.  TOWER. 


Tabi,E  I. 


Nickel  tartrate. 

Cobalt  tartrate. 

V. 

M.  v. 

M.' 

V. 

M. 

V. 

mP 

10.35 

9-2  I3-46 

12.0 

25.38 

25-4 

31-05 

32.2 

2 X IO.35 

13.8  2XI3-46 

16.4 

2 X 25.38 

34-5 

2X3!-05 

43-o 

4 X 10.35 

20.7  4XI3-46 

22.7 

4 X 25.38 

47-4 

4 X 31-05 

57-i 

8 X 10.35 

30.6  8XI3-46 

29.8 

8 X 25.38 

63-5 

8X31-05 

74-4 

16  X 10.35 

44.4  T6XI3-46 

45-o 

16  X 25.38 

83.2 

16X31-05 

96.0 

32  X 10.35 

62.8  32X13-46 

61.2 

32X25.38 

105.6 

32X31-05 

120.6 

64  X 10.35 

81.5  64XI3-46 

81.3 

64  X 25.38 

i33-o 

64X31-05 

150.2 

Magnesium  tartrate. 

Barium  tartrate. 

V. 

M.  v. 

M.  ' 

V. 

M. 

V. 

M. 

19-95 

67.4  24.37 

7I.9 

20.03 

58.5 

21.27 

59-3 

2 X 19-95 

82.0  2 X 24.37 

87.7 

2 X 20.03 

70.4 

2 X 21.27 

72.8 

4 X 19-95 

98.I  4X24.37 

103.0 

4 X 20.03 

85.2 

4X21.27 

88.6 

8 X 19-95 

114.6  8X24.37 

II9.2 

8 X 20.03 

105. 1 

8X21.27 

106.4 

16  x 19-95 

130.5  16  X 24.37 

135. 1 

16  X 20.03 

125.6 

l6X  21.27 

126.5 

32  X 19-95 

145.8  32X24.37 

150.0 

32  X 20.03 

143.O 

32X21.27 

147-3 

64  X 19-95 

160.7  64X24.37 

165.9 

64  X 20.03 

161.4 

64  X 21.27 

167.1 

Manganese  tartrate. 

Nickel  malate.1 

Cobalt  malate. 

V. 

M.  v. 

M.  ^ 

V. 

M. 

V. 

M. 

37-79 

66.9  4I.71 

68.8 

14-77 

14.5 

18.44 

23.6 

2X37.79 

81.5  2X41.71 

83.8 

2X14.77 

17.7 

2 X 18.44 

28.8 

4X37-79 

98.5  4X4I-71 

99-7 

4 X 14.77 

22.0 

4 X 18.44 

36.0 

8X37-79 

II4.5  8X41.71 

117.0 

8 X 14.77 

28.2 

8 X 18.44 

45-2 

16X37.79 

132.5  16  x 41.71 

133-5 

i6Xi4.77 

37-1 

16  x 18.44 

58.1 

32X37.79 

148.3  32X41.71 

148.9 

32  X 14-77 

51.0 

32  X 18.44 

74.6 

64  x 14.77 

69-9 

64  X 18.44 

94-3 

Magnesium  malate. 

Nickel  succinate. 

V. 

M. 

V. 

M. 

V. 

M? 

9-74 

43-3 

18.42  62.2 

19-57 

62.7 

2X9-74 

54-7 

2 X 18.42  75-9 

2 X 19-57 

76.9 

4 X 9-74 

67.4 

4X18.42  9I.7 

4 X 19-57 

92.5 

8 X 9-74 

83.0 

8 X 18.42  108.8 

8 X 19-57 

109.5 

16X9-74 

IOO.  I 

16X18.42  125.9 

16  X 19-57 

126.6 

32  X 9-74 

118.3 

32  X 18.42  143.0 

32  X 19-57 

145-2 

64  X 9-74 

135.0 

64X18.42  158.4 

64X19-57 

160.3 

128  + 9.74 

149.O 

Cobalt  succinate. 

Magnesium  succinate. 

V. 

M.  v. 

M. 

V. 

M. 

V. 

mP 

17.29 

65.0  20.25 

68.2 

14.31 

76.6 

15.70 

77.6 

2 X 17.29 

78.3  2X20.25 

82.2 

2 X 14.31 

88.7 

2 X 15.70 

90.0 

4 X 17.29 

93.O  4X20.25 

97.1 

4 X 14.31 

102.8 

4 X 15.70 

104.2 

8 X 17-29 

Io9-7  8X20.25 

113.6 

8 X 14.31 

117.4 

8 X 15.70 

119.8 

16  X 17-29 

126.6  16X20.25 

130.2 

16  X 14-31 

131-9 

16X15-70 

134.6 

32  X 17-29 

145-0  32X20.25 

148.0 

32  X 14-31 

146.2 

32  X i5-7o 

149.0 

64  X 17.29 

159.0  64X20.25 

162.3. 

64  X 14.31 

158.8 

64  x 15.70 

160.8 

1 ?nl7  on?  solution  of  each  salt  of  malic  acid  could  be  prepared  with  the  small  quan- 
tity of  this  acid  on  hand. 


ORGANIC  SALTS  OF  NICKEL  AND  COBALT. 


IOI5 


From  these  results  interpolations  have  been  made  graphically 
foi  v.—  16,  32,  etc.,  by  plotting  curves  with  the  molecular  con- 
ductivities as  abscissas  and  the  logarithms  (base  2)  of  the  dilu- 
tions, v,  as  ordinates.  The  interpolated  values  are  given  in  Table 
II.  In  cases  where  the  conductivity  was  determined  in  two 
separate  solutions  only  the  average  is  given  in  the  table.  The  re- 
sults of  Walden1  for  magnesium  salts  of  these  acids  are  given  for 
comparison.  They  have  been  reduced  to  the  same  units  and 
temperature.  The  temperature  coefficient  used  for  this  purpose 
was  0.027,  the  average  value  found  by  Arrhenius2  for  sodium  salts 
of  organic  acids. 


Table  II. 

Molecular  conductivity  of  tartrates. 

Mag-  Magnesium. 

v.  Nickel.  Cobalt,  nesium.  (Walden.)  Barium.  Manganese. 

16 12.3  ....  63.0  

32 18.1  30.5  77.5  ....  66.8  63.2 

64 25.8  41. 1 93.0  92.3  81.2  78.0 

128 37.1  55.5  109.8  107.8  98.5  94.2 

256 52.0  72.4  125.5  124.5  II7-3  no. 7 

512 70.4  94.2  140.8  138.9  136.2  127. 1 

1024 93.0  118.0  156.0  151.5  155.0  143.9 

Molecular  conductivity  of  malates. 

Magnesium. 

r.  Nickel.  Cobalt.  Magnesium.  (Walden.) 

l6 14.8  22.8  51. 1 

32 l8.I  27.8  63.6  

64  22.6  34.2  78.2  80.9 

128 29.3  43.O  95.O  96.9 

256  38.5  55.2  II3.4  II3.9 

512  53.O  7O.7  129.2  I30.5 

1024  72.3  9O.3  I46.O  I45. 1 

Molecular  conductivity  of  succinates. 

Magnesium. 

v.  Nickel.  Cobalt.  Magnesium.  (Walden.) 

16 59-5  63.7  78.2 

32 73-o  76.8  90.7 

64  88.0  91.2  104.8  106.8 

128  105.2  107.9  120.2  121.6 

256  122.3  I24-6  134.7  135.6 

512  139.7  142.4  148.9  147-8 

io24 155.6  157-5  l6o-s  158.6 


1 Ztschr.  phys.  Chern i,  537  (1887). 

2 Ibid.,  4,  99  (1889). 


ioi6 


O.  F.  TOWER. 


The  molecular  conductivities  of  the  tartrates  of  magnesium, 
barium  and  manganese  do  not  vary  from  one  another  more  than 
may  be  expected  for  different  salts  of  the  same  acid.  The  con- 
ductivities of  the  tartrates  of  nickel  and  cobalt  are,  however,  so 
small  as  to  be  of  an  entirely  different  order.  The  same  is  true  of 
the  conductivities  of  the  malates  of  nickel  and  cobalt.  The  con- 
ductivity of  magnesium  malate  is  somewhat  less  than  that  of  the 
tartrate,  as  was  also  observed  by  Walden.  The  conductivities  of 
the  succinates  of  nickel  and  cobalt  present  no  abnormal  behavior 
when  compared  with  the  conductivity  of  magnesium  succinate. 

Determinations  of  the  lowering  of  the  freezing-point  were  made 
with  the  apparatus  described  in  my  former  article.  Determina- 
tions of  the  freezing-point  of  the  same  solution  never  varied  more 
than  o.ooi°,  but  the  freezing-points  of  two  solutions  made  up  as 
nearly  alike  as  possible  gave  larger  differences.  Since  the  solu- 
tions used  were  rather  dilute,  a difference  of  two  or  three 
thousandths  of  a degree  would  frequently  make  a difference  of  ten 
or  twenty  units  in  the  molecular  weights  calculated  from  them. 
So  much  reliance  cannot  therefore  be  placed  on  the  absolute  or  on 
the  relative  value  of  the  results  obtained  by  this  method,  as  on 
those  obtained  by  measuring  the  electrical  conductivity.  The 
depressions  of  the  freezing-point  together  with  the  apparent 
molecular  weights  calculated  from  them  are  given  in  Table  III. 


Table  III. 


Nickel  tartrate. 

Cobalt  tartrate. 

Substance  in 
IOO  cc. 
Grams. 

Depression . 

Apparent 
mol.  wt. 

Substance  in 

100  cc.  Apparent 

Grams.  Depression.  mol.  wt. 

I.8795 

0.139° 

260 

O.6739 

0.062° 

207 

1.7205 

0.121 

273 

0.6505 

0.059 

207 

I.6450 

0.117 

268 

O.3370 

0.037 

173 

0.8602 

0.081 

202 

0.3252 

0.036 

170 

0.8225 

0.076 

206 

0.1685 

0.021 

153 

O.430I 

0.042 

193 

O.1626 

0.021 

146 

Magnesium  tartrate. 

Barium  tartrate. 

0.8642 

0.139° 

Il8 

0.7136 

0.063° 

216 

0.8428 

0.137 

117 

0.3568 

0.036 

189 

0.4321 

0.079 

104 

0.3568 

0.039 

174 

0.4214 

0.076 

106 

0.1784 

0.020 

170 

0.2160 

0.045 

91 

0.1784 

0.021 

162 

Manganese  tartrate. 

Nickel  malate. 

0.6130 

0.083° 

141 

I. 2912 

0.147° 

167 

ORGANIC  SALTS  OF  NICKEL  AND  COBALT. 


1017 


Manganese  tartrate. 

Nickel  malate. 

Substance  in 

Substance  in 

IOO  cc. 

Apparent 

IOO  cc. 

Apparent 

Grams. 

Depression. 

mol.  wt. 

Grams. 

Depression. 

mol.  wt. 

O.5805 

0.078° 

142 

0.6456 

0.086° 

143 

0.3075 

0.046 

127 

O.3228 

O.050 

123 

O.2902 

O.041 

135 

Cobalt  malate. 

Magnesium  malate. 

I.0360 

0.114° 

173 

I.6060 

0.244° 

125 

0.5180 

0.068 

144 

0.8030 

0.130 

Il8 

O.259O 

0.040 

123 

O.4015 

0.079 

97 

Nickel  succinate. 

Cobalt  succinate. 

0.9488 

0.169° 

107 

I.OI25 

0.176° 

no 

O.893I 

0.160 

106 

0.8646 

0.156 

106 

O.4744 

0.095 

95 

O.5062 

0.094 

103 

0.4466 

0.082 

104 

0.4323 

0.084 

98 

O.2233 

0.049 

87  . 

O.253I 

0.057 

85 

Magnesium  succinate. 

0.9808 

0.207° 

90 

0.8942 

0.185 

81 

0.4904 

0.115 

8r 

0.4471 

0.098 

76 

0.2452 

0.065 

72 

In  order  to  render  tjiese  results  more  readily  comparable,  by 
means  of  graphical  interpolation  the  molecular  weights  have  been 
calculated  for  dilutions  of  16  and  32  liters.  These  figures  together 
with  the  molecular  weights  calculated  from  the  simple  formulas 
of  the  respective  salts  are  given  in  Table  IV. 


Table  IV. 

Tartrates. 


Malates.  Succinates. 


Mol.  wt.  from  formula 

Values  interpo-  ( . . 

lated  from  \ ^ ‘ 

Table  III  |^  = 32*-- 


207  207  172  286  203 


230  244  122  

196  207  109  234  143 


3 


191  191  156 


164  179  120 
140  150  100 


3 

3 


175  175  140 


108  hi  82 
100  103  77 


From  this  table  it  is  seen  that  all  the  salts  yield  in  the  more  con- 
centrated solutions  apparent  molecular  weights  considerably  less 
than  the  molecular  weights  calculated  from  the  formula,  except 
the  tartrates  and  possibly  the  malates  of  nickel  and  cobalt.  Ac- 
cording to  the  dissociation  theory  we  should  expect  all  of  the  salts 
in  solutions  of  this  concentration  to  give  apparent  molecular 


ioi8 


O.  F.  TOWER. 


weights  much  less  than  the  true  ones.  The  nickel  and  cobalt  salts 
just  mentioned,  which  give  such  high  molecular  weights,  are  the 
ones  calling  for  special  explanation.  These  exceptional  results 
yielded  by  the  freezing-point  method  are,  however,  in  line  with 
the  conductivity  determinations  with  the  same  salts. 

An  adequate  explanation  of  this  peculiar  behavior  of  the  tar- 
trates and  malates  of  nickel  and  cobalt  is  difficult  to  find.  It  was 
Walden1  who  first  pointed  out,  working  with  magnesium  salts, 
that  the  dissociation  of  the  salts  of  dibasic  acids  with  bivalent 
metals  as  measured  by  the  conductivity  was  of  a very  different 
nature  from  the  dissociation  of  the  neutral  sodium  salts  of  the 
same  acids.  Bredig2  has  attempted  to  explain  this  difference  on 
the  assumption  that  the  molecules  of  a salt,  MgAc  (Ac  being  the 
radical  of  a dibasic  acid),  split  up  into  complex  ions  of  the  nature 

Mgx  /Ac 

+ >Ac  and  Mg\  — 

Mg/  XAc 

as  well  as  the  simpler  ones  Mg  and  Ac.  As  the  dilution  increases 
the  complex  ions  gradually  tend  to  decompose  into  the  simpler 
ones.  The  behavior  of  nickel  and  cobalt  tartrates  and  malates  has 
been  shown  to  be  very  different  from  that  of  the  magnesium  salts 
of  the  same  metals.  The  suggestion  was  made  in  the  article  to 
which  reference  has  already  been  made,  that  the  abnormal 
behavior  of  the  tartrates  of  nickel  and  cobalt  might  be  ascribed  to 
polymerization  of  the  molecules.  The  same  would  also  apply  to 
the  malates.  The  molecule  of  nickel  tartrate,  for  example,  in 
solution  would  have  the  formula 

COONiOOC 

I I 

CHOH  CHOH 

I I 

CHOH  CHOH 

I I 

COONiOOC 

and  would  be  dissociated  in  concentrated  solutions  into  complex 
ions  and  as  dilution  proceeds  into  simpler  ones  in  a manner  similar 
to  that  indicated  above  for  magnesium  salts,  the  dissociation,  how- 

1 Loc.  cii.,  p.  529,  el  seq. 

2 Ztschr.  phys.  Client.,  13,  202  (1894). 


ORGANIC  SALTS  OF  NICKEL  AND  COBALT. 


IOig 


ever,  being  much  less.  This  explanation  differs  from  that  of 
Bredig  for  magnesium  salts  in  assuming  the  existence  of  double 
molecules  in  solution  as  well  as  of  complex  ions,  and  seems  to 
have  support  in  the  apparent  molecular  weights  derived  from  the 
freezing-point  method. 

The  application  of  Ostwald’s  formula  for  basicity,  as  developed 
by  Walden1  for  dibasic  salts  of  bivalent  metals,  throws  but 
little  light  on  this  question.  The  formula  is  A — Cnpi^  where  A 
is  the  difference  between  the  equivalent  conductivities  at  v — 32 
and  v = 1024,  nx  is  the  basicity  of  the  acid  radical,  n2  is  the 
valence  of  the  metal,  and  C is  a constant,  equal  usually  to  10  or  a 
little  less.  Only  molecular  conductivities  are  given  in  Table  II  so 
that  the  difference  between  the  values  at  v — 32  and  v — 1024 
must  be  divided  by  two  to  make  it  comparable  with  the  difference 
obtained  with  equivalent  conductivities.  When  this  is  carried  out 
for  the  nickel  and  cobalt  salts  the  basicity  is  found  to  be  two,  just 
the  same  as  when  applied  to  the  magnesium  salts.  Since,  how- 
ever, the  formula  is  wholly  empirical,  the  results  obtained  by 
using  it  cannot  be  accepted  without  other  support  in  the  face  of 
the  values  derived  by  the  freezing-point  method.  If  the  Ostwald 
rule  shows  anything  in  this  instance,  it  is  rather  to  be  interpreted 
as  indicating  that  the  complex  ions  decompose  but  little  below  the 
dilution,  1024.2 

If  then  the  tartrates  and  malates  of  nickel  and  cobalt  are 
polymerized  in  aqueous  solution,  the  molecules  of  the  succinates 
are  surely  not,  for  their  conductivities  are  normal  and  the  apparent 
molecular  weights  found  by  the  freezing-point  method  also  pre- 
clude any  such  condition.  This  seems  to  show  that  the  presence 
of  the  hydroxyl  groups  in  the  tartaric  and  n?alic  acids  may  have 
some  influence  in  inducing  polymerization  of  the  nickel  and  cobalt 
salts.  There  appears  to  be  ground  for  this  in  the  fact  that  the 
results  obtained  with  the  tartrates  reveal  a greater  degree  of 
polymerization  than  those  with  the  malates ; that  is,  the  polymer- 
izing influence  is  apparently  greater  where  two  hydroxyl  groups 
are  present  than  where  only  one  is  present. 

1 Loc.  cit. 

2 From  the  electromotive  force  of  a cell  containing  a 1/5 0 molecular  solution  of  nickel 
tartrate  only  about  one-tenth  of  the  nickel  was  found  to  exist  in  the  ionic  state.  Tower  : 
Loc.  at..  p.  511. 


1020 


O.  F.  TOWER. 


That  the  presence  of  an  hydroxyl  group  is  the  determining  in- 
fluence in  causing  polymerization  of  the  nickel  and  cobalt  salts 
receives,  however,  no  support  from  the  results  obtained  by  apply- 
ing methods  similar  to  the  above  to  the  malonates  and  tartronates 
of  nickel  and  cobalt.  Conductivity  and  freezing-point  determina- 
tions were  carried  out  with  these  salts  and  also  with  the  magne- 
sium salts  of  the  same  acids.  The  malonic  acid  was  a preparation 
of  Merck.  The  tartronic  acid  was  made  from  dinitrotartaric  acid 
according  to  Demole.1  The  yield  was  small,  which  accounts  for 
only  one  set  of  determinations  having  been  made.  Molecular  con- 
ductivities are  given  in  Table  V,  and  depressions  of  the  freezing- 
point  in  Table  VI. 


Table  V. 


Nickel  malonate.  Cobalt  malonate. 


V. 

M. 

v.  M. 

V. 

M. 

V. 

M. 

15.61 

23.7 

20.55  23.3 

12.82 

28.5 

19.17 

30.6 

2 X 15.61 

27.3  2 X 20.55  26.9 

2 X 12.82 

33-2 

2 X i9-I7 

35-7 

4 X 15-61 

32.1  4X  20.55  31.8 

4 x 12.82 

39-6 

4 X 19.  J7 

42.4 

8 X 15-61 

39.9  8X20.55  39.O 

8 X 12.82 

48.6 

8 X 19-17 

52.3 

16  X 15-61 

49.4  16  X 20.55  49.5 

16  X 12.82 

61. 1 

16  X 19.17 

64.9 

32  X 15.61 

64.0  32  X 20.55  64.0 

32  X 12.82 

78.4 

32  X I9-I7 

81.5 

64  X 15.61 

80.2 

64  x 12-82 

96.0 

Magnesium  malonate. 

Nickel  tartronate. 

V. 

M. 

V. 

M. 

V. 

M. 

8.02 

34.6 

1 1. OO 

38.2 

30.50 

29.7 

2 X 8.02 

42.7 

2 X II. OO 

47.1 

2 X 30.50 

34-7 

4 X 8.02 

51-7 

4 X 1 1. 00 

59-2 

4 X 30.50 

40.3 

8 X 8.02 

64.7 

8 X 1 1. 00 

73-2 

8 X 30.50 

46.9 

16  X 8.02 

77-5 

16  X 11. 00 

88.7 

16X30.50 

54-5 

32  X 8.02 

93-8 

32  X 1 1 .00 

106.9 

32  X 30.50 

63.8 

64  X 8.02 

110.9 

64  X 11. 00 

126.8 

Cobalt  tartronate. 

Magnesium  tartronate. 

V. 

M. 

V. 

M. 

28.10 

36.5 

15-77 

42.O 

2 X 28.IO 

43-3 

2 X 15-77 

51-3 

4 X 28.10 

50.6 

4 X 15-77 

61.9 

8 X 28. 10 

58.7 

8 X 15.77 

74-8 

16  x 28.10 

68.5 

16  x 15.77 

89.2 

32  X 28.10 

79*4 

32  X J5-77 

105.7 

64  X 15-77 

122.5 

1 Ber.  d.  1 

them.  Ges.,  10, 

1789  (1877). 

ORGANIC  SALTS  OP  NICKEL  AND  COBALT. 


1021 


TABLE  VI. 

Nickel  malonate. 


Substance  in 

100  cc. 

Apparent 

Grams. 

Depression. 

mol.  wt. 

I.0300 

O.1500 

131 

C.7824 

O.141 

106 

0.5150 

0.090 

109 

0.2575 

O.054 

91 

Magnesium  malonate. 

1.5750 

O.298 

101 

1.1477 

O.233 

94 

0.5738 

0.134 

82 

0.2869 

0.075 

73 

Cobalt  tartronate. 

0.6302 

0.119 

101 

0.3151 

0.071 

85 

0.1576 

0.043 

70 

Cobalt  malonate. 


Substance  in 
100  cc. 
Grams. 

Depression. 

Apparent 
mol.  wt. 

i -1995 

0.201° 

114 

0.8402 

O.169 

95 

0.5998 

O.H5 

99 

0.2999 

O.066 

86 

Nickel  tartronate. 

0.5798 

0.102 

108 

0.2899 

O.065 

85 

0.1450 

O.O39 

7i 

Magnesium  tartronate. 

0.9944 

0.200 

95 

0.4972 

O.I2I 

78 

0.2486 

O.072 

66 

To  bring-  the  results  of  these  two  tables  to  a uniform  basis, 
interpolations  have  been  made  graphically,  exactly  as  in  the  pre- 
ceding cases.  These  interpolated  values  will  be  found  in  Tables 
VII  and  VIII. 


Table  VII. 

Molecular  conductivity. 

, s 

Malonates.  Tartronates. 


V . 

Nickel. 

Cobalt. 

Magne- 

sium. 

Magnesium. 

(Walden.) 

Nickel. 

Cobalt. 

Magne- 

sium. 

l6 

23.O 

30.0 

43*o 

.... 

25.5 

32.0 

42.3 

32 

26.5 

34.7 

52.6 

.... 

29.9 

37.8 

51.5 

64 

3I.2 

41.2 

65.7 

62.9 

35-i 

44-7 

62.4 

128 

38.2 

51.2 

79-5 

77-5 

40.8 

52.2 

75-3 

256 

47-8 

64.0 

95-9 

95-4 

47-3 

60.3 

89.9 

512 

80.4 

IT3-9 

II4.7 

59-2 

70.4 

106.3 

1024 

77-2 

99*3 

i35.o 

134.9 

64.3 

81.2 

123.0 

Table  VIII. 

Malonates.  Tartronates. 

, » ^ ( A „ 

Magne-  Magne- 

Nickel.  Cobalt,  sium.  Nickel.  Cobalt,  sium. 

Molecular  weight  from  formula 161  161  126  177  177  142 

• Values  interpolated  (v=  16 121  104  87  94 

from  Table  V.  \z;  = 2>2 101  91  77  106  98  77 

It  is  seen  in  these  cases  as  heretofore,  that  the  nickel  and  cobalt 
salts  possess  lower  molecular  conductivities  and  higher  apparent 
molecular  weights  than  the  corresponding  magnesium  salts.  Al- 


1022 


ORGANIC  SALTS  OF  NICKEL  AND  COBALT. 


though  the  conductivities  of  all  these  salts  are  less  than  for  the 
corresponding  succinates,  still  the  relative  differences  between  the 
conductivities  of  the  nickel,  cobalt,  and  magnesium  salts  are  about 
the  same  as  in  the  case  of  the  succinates.  No  such  differences 
exist,  as  were  found  between  the  conductivities  of  the  tartrates 
and  malates  of  magnesium  and  those  of  the  corresponding  nickel 
and  cobalt  salts.  The  conductivities  of  the  magnesium  salts  of 
malonic  and  tartronic  acids  are  considerably  less  than  the  con- 
ductivities of  any  of  the  other  magnesium  salts  investigated.  This 
was  noticed  by  Walden  in  the  case  of  the  malonate.  B redig’s  ex- 
planation of  such  behavior  has  already  been  referred  to.  The  im- 
portant point  to  notice  in  connection  with  these  last  results  is, 
however,  that  the  conductivities  of  the  nickel  and  cobalt  tartron- 
ates  are  not  appreciably  less  than  the  conductivities  of  the  same 
malonates,  although  tartronic  acid  possesses  an  hydroxyl  group. 
Any  explanation  of  the  conduct  of  these  salts  based  on  the  pres- 
ence of  an  hydroxyl  group  in  the  molecule,  therefore,  appears  to 
be  untenable. 

Before  letting  the  question  rest  here,  however,  a few  consider- 
ations bearing  upon  the  point  under  discussion  will  be  mentioned. 
The  strength  of  the  acids  of  the  succinic  acid  series  (i.  e.,  succinic, 
malic,  and  tartaric  acids),  as  is  well  known,  increases  with  the 
number  of  hydroxyl  groups  present,  Ostwald’s  affinity  constants 
being  for  succinic  acid  0.0066,  for  malic  acid  0.0395,  f°r  tartaric 
acid  0.097. 1 The  hydroxyl  groups  have  therefore  a distinct  effect 
on  the  strength  of  the  acids.  In  the  case  of  malonic  and  tartronic 
acids  a very  different  effect  is  observed.  The  Ostwald  constant  for 
malonic  acid  is  0.158  and  for  tartronic  acid  0.107 ; that  is,  the  intro- 
duction of  an  hydroxyl  group  has  here  decreased  the  strength  of 
the  acid.  Such  being  the  facts  with  regard  to  the  acids,  it  seems 
probable  that  salts  of  the  succinic  acid  series  might  show  very 
different  gradations  in  properties  from  the  same  salts  of  the 
malonic  acid  series.  Then  before  asserting  that  the  presence  of 
the  hydroxyl  groups  in  malic  and  tartaric  acids  has  no  effect  on 
the  behavior  of  their  nickel  and  cobalt  salts,  it  is  necessary  to  ex- 
tend investigations  similar  to  these  to  the  salts  of  the  glutaric  acid 
series  or  some  higher  one.  Such  work  is  contemplated  in  the 
future. 

1 The  values  given  are  for  K = 100L  See  Ztschr.  phys.  them 3,  418  (1889). 


ORGANIC  SALTS  OF  NICKEL  AND  COBALT. 


1023 


Iii  conclusion,  however,  it  may  be  stated  that  aqueous  solutions 
of  nickel  and  cobalt  salts  of  dibasic  organic  acids  offer  greater 
resistance  to  the  passage  of  the  electric  current  than  solutions  of 
similar  salts  of  the  other  metals  investigated,  notably  magnesium, 
and  that  this  resistance  is  exceptionally  great  in  the  case  of  the 
tartrates  and  malates  of  nickel  and  cobalt.  This  abnormal  be- 
havior of  the  last-named  salts  is  also  confirmed  by  the  results  ob- 
tained with  the  freezing-point  method  for  determining  molecular 
weights. 

Western  Reserve  University, 

Cleveland,  O.,  June,  1902. 


